Cold storage units such as freezers and dewars are used for various purposes, including the storage of biological samples over short and long periods of time. For example, biological materials for transplantation such as blood, tissue, or plasma may require storage for short periods of time before use. In another example, biological cells such as DNA samples may be stored for longer periods of time. Conventional cold storage units may be cooled by mechanical refrigeration circuits or by other methods, including the provision of liquid nitrogen (“LN2”). One type of cold storage unit used to store biological samples is known as an “ultra-low temperature freezer” (“ULT”), which is used to cool its inner storage chamber to relatively low temperatures such as about −80° C. or lower, for example.
Known cold storage units are configured to contain a plurality of storage boxes supported on different types of storage racks within a cooled cabinet. One type of storage rack referred to as a sliding drawer storage rack is configured to contain a plurality of storage boxes and provide access to these storage boxes via sliding a drawer out from the storage rack. To this end, these sliding drawer storage racks include a rack body with first and second sidewalls and a plurality of shelves extending across the space between the first and second sidewalls. A plurality of drawers are slidably supported on each of the shelves, each drawer sized to hold a line or series of storage boxes lined up within a storage cavity defined by the drawer. The storage boxes are lined up along a central longitudinal axis of the drawer, which also defines a sliding movement direction of the drawer when a user moves a drawer to obtain access to the storage boxes stored therein. While material selection may vary, storage racks for cold storage units are often manufactured from either stainless steel or aluminum.
Although apertures are cut into each of the shelves and the rack body, the sliding drawer storage rack requires a significant amount of material to produce each of the shelves and drawers so as to extend across the entire width of the rack body. Furthermore, the frictional engagement of the drawers on the corresponding shelves can be difficult to overcome should the drawers freeze to one or more of the shelves during storage in the cryogenic temperatures of the cold storage unit. If the storage cavity of a particular drawer is not completely filled with storage boxes, the boxes that are stored in the drawer may slide along the length of the drawer during movement of the drawer. This uncontrolled sliding movement may make it more difficult to retrieve storage boxes that slide to the rear end of the storage rack and may also jostle the samples or materials held within the storage boxes.
There is a need, therefore, for a sliding drawer storage rack for use with a cold storage unit that reduces material weight necessary during assembly while providing improved performance compared to conventional storage racks.